Previously, as a sealing material of a wall material of buildings, a gasket of a lamp cover of automobiles, or a cushioning material of an automobile door material, a polyurethane foamed sheet has been used, but there is a problem that a polyurethane foamed sheet is degraded with a moisture in the air, or is deteriorated with ultraviolet-ray.
Then, Patent Document 1 proposes a method for producing a crosslinked polyolefin open cell body, comprising a step of molding a foamable crosslinking composition obtained by adding a foaming agent and organic peroxide to a polyolefin-based resin, into a desired shape at a prescribed temperature in the state of a gel fraction of zero, a step of heating this molded foamable crosslinking composition under a normal pressure to perform degradation of organic peroxide and a foaming agent simultaneously, to form a foam, and a step of applying mechanical deformation to this foam to communicate cells.
However, since the aforementioned method for producing a crosslinked polyolefin open cell body requires a complex crosslinking/foaming step; thus, there arises a problem of poor production efficiency. Further, the obtained crosslinked polyolefin open cell body has a problem that a non-foamed layer formed on a surface thereof is hard; therefore, a flexibility lacks.
Patent Document 1: JP-B-62-19294